Converts a string into a slug. JS and PHP versions.

str_to_slug.js

function str_to_slug(str, sep) {
    if (typeof sep == 'undefined') {
        sep = '-';
    }
    
    // remove extra spaces and convert to lowercase
    str = str.toString().trim().toLowerCase();
	// convert any character that's not alphanumeric into a separator
	str = str.replace(/[^a-z0-9]/g, sep)
	// replace any successive separators with a single one
	var duplicate_seps_regex = new RegExp(sep+'+', 'g');
	str = str.replace(duplicate_seps_regex, sep);
	// remove any hanging separators at the end of the string and return
	var rtrim_regex = new RegExp(sep+'*$', 'g');
	return str.replace(rtrim_regex, "");
	
}

str_to_slug.php

<?php

function str_to_slug( $str, $sep='-' ) {
	// remove extra spaces and convert to lowercase
	$str = strtolower(trim($str));
	// convert any character that's not alphanumeric into a separator
	$str = preg_replace('/[^a-z0-9]/', $sep, $str);
	// replace any successive separators with a single one
	$str = preg_replace('/'.$sep.'+/', $sep, $str);
	// remove any hanging separators at the end of the string and return
	return rtrim($str, $sep);
}